The jury discounted the defense account that Stromberg, a part-time actor and sometime horror-film producer, was insane when he grabbed a knife; packed a bag with a nightstick, hammer and two swords; and burst into his wife's apartment on West Walnut Lane just before 8 p.m. on April 28, 1996.
Looking grim and disheveled, Stromberg stood hunched over at the defendant's table next to his lawyer as the verdicts were read. His eyes were downcast. He did not look back at his family members, who remained stoic and did not weep. Stromberg also did not see Stefan's family and friends quietly hug.
After the verdicts were read, the victims' and defendant's families quickly left the Criminal Justice Center courtroom without commenting.
The jury will return Monday to hear evidence and arguments from lawyers over whether Stromberg should be given the death penalty or life in prison without parole.
Assistant District Attorney Carlos Vega, who prosecuted the case, contended that the double-slayings followed a stormy marriage in which Stromberg controlled and abused his wife and ``took all her money.''
Stromberg's attorney, Nino V. Tinari, admitted that Stromberg slashed the two women 34 times but said his client descended into ``madness'' and became the monster in one of his horror movies after learning of his wife's affair the previous fall, her pregnancy and abortion.
``This man, beginning from a very young age, was crazy,'' Tinari said said in his closing statement.
At one point, the jury viewed a videotape of an interview Stromberg made - days after he had been charged - with the TV news program Hard Copy.
``Did he look like he was crazy?,'' Vega asked the jurors. ``He knew what he was saying. He was talking very coherently, setting up his defense. He's an actor, and he doesn't want to go to jail.''
Stromberg's mental state before, during and after the slayings was the central issue of the trial.
A psychiatrist, Julie B. Kessel, testified for the defense that Stromberg suffered from chronic psychotic illness and could not form the ``specific intent to kill.'' When Stromberg ran into the house, he did not intend to kill the two women and did not know the difference between right and wrong, Kessel said.
That assertion was rebutted by a psychiatrist for the prosecution, John S. O'Brien.
The defendant was ``playing a role of someone who was mentally impaired, as opposed to someone who is mentally impaired,'' said O'Brien, adding that Stromberg ``meets the profile of a spouse abuser.''
The prosecutor said Stromberg's actions after the stabbings - taking the No. 23 bus to Chestnut Hill, washing his face and hands at the Borders bookstore there, and roaming the woods two days before surrendering to police - was further evidence that he was sane.
``He's not insane. He's evil,'' Vega said. ``This is the biggest role of his life. If he doesn't do a good job, he doesn't go home.''
Stromberg, in a statement to police read to the jury, said that he flew into a rage because he suspected Stefan was cheating on him.
On the night before the killings he had cried in his wife's arms for 45 minutes, and ``we were going to try to make the marriage go,'' he told police.
The next evening, after not hearing from his wife, Stromberg said he ``lost control,'' packed a bag with weapons, took the bus to Germantown, and ran across the back yard to his wife's apartment. Then he burst in. Stefan was by the counter in the kitchen; his mother-in-law was standing by a microwave.
``They turned. They screamed. I was swinging. They were hitting me. I was hitting back. I was swinging the knife.''